Strategy to book last minute flights

Guys

I'm heading to europe right after labor day and returning mid-sept. Unfortunately no successful alerts on expertflyer as yet. I want to validate my strategy here (all my hotels are booked with cancellation possible 1 day prior to check-in)

I've been checking flights for NYC-Paris coach non-stop last few days on both United and AA and each day at least 2 seats become available anywhere from 1-3 days before departure. And this is still a peak time for Europe travel

I'm relying on the above data to wait till the day of departure. If I get unlucky, worst-case I'll just book a cash flight and calling my agent, she was again able to find something for $700

Is this strategy valid? I know there are inherent risks but given Sept is lower flying period than Aug, I think my chances are good

I could alternatively book 1-stop flights and change to non-stop but I'll be paying a $75 fee right now given I'm 21 days within departure and think I have to pay another $75 even if my city pairs are the same (don't have elite status)

Given I have alerts set up on experflyer, can you kindly rate my chances with 1 being worst and 10 being it should work

Also, are there any sites that cater to super last minute flights?

Thank you!